Manufacture of sulphuric acid



Patented Nov. 18, 1930 UNITED STATES HUGO PETEBSEN, 0F BEBLIN-STEGLITZ, GERMANY MANUFACTURE 0F SULPHURIC ACID Application lcd February 24, 1927, Serial No. 170,663, and in Germany latch 20, 1926. l

This invention has reference to improvements in the manufactural of .sulphuric acid by means of the oxidizing action of nitrogen oxids, and it refers more partirularly to the methods of producing high-grade sulphuric' acid without the use of leadrhalnbvrs and by the use of nitrosulplmniv or nitrosyl-sulphuric acid or of so-called nitrous vitriol as the main oxidizing agent, and among other important objects, it is intended to increase the intensity and efficiency of the several working units and to accordingly limit the number and extension thereof. In view thereof the oxidation of the gases of sulphurdioxid or of sulphurous acid is considerably accelerated by providing foran undecomposed excess of free nitrosulphonic acid, for which purpose the strength of the nitrosuL phonic lacid employed in the several units or enclosures is correspondingly regulated or, in the case of rinsing them with comparatively weak nitrosulphonic acid or nitrous vitriol, such increased amounts thereof are employed that in the parts of the plant employed for the production of the sulphuric acid itself a very highoxidizing eiliciency is Vobtainedwith but a verylimited amount of liberation of nitrogen oxids, so that the rinsing nitrosulphonic acid or nitrous vitriol leaving said enclosures, will still be very high in available nitric oxids. Now I have ascertained in the further course of my investiga- "tions that this object will be most readily accomplished with a greatreduction in the quantity of the nitrosulphonic rinsing acid, if enclosures of certain height and cross section are employed, and preferably with 'the simultaneous employment of a particularly suitable kind of packing or filling material. By operating in this manner it has become posslble to so regulate the manner of operation of the plant that the ratio o f the nitrogen oxids liberated in the production enclosures from the nitro-sulphonic acid, ex ressed in terms of nitric acid of 36 degrees to the amount of sulphuric acid produced, and expressed in terms of sulphuric acid Y will be so much reduced that one part of libegated`36 B. nitric acid will correspond up t6 2O and more parts off-:sulphuric acidof 60 B. But there will already he a great advantage if this proportion would onl be 3 1'. As regards the reaction enclosures t ley may preferably comprise towers or tower-like pieces of apparatus.

In order to arrive at the oxidizing capacity of the nitrosnlphonic acid above referred to it is of importance to impart certain dimensions to the reaction enclosures of the plant.

The cross sectional area of the several units 69 should be regulated in accordance with the more than six (6 millimeters) millimeters 70 water column for each vertical or ascending meter, inasmuch as otherwise the resulting friction would necessitate too much power for the movement of the gases, which wouldinterfere with the judicious and economical working of the process. The height of the enclosures will be governed by the cross sectional area employed, and such'height may amount to 18 meters (59 feet) and even more.

One single production enclosure will be suicient for the purpose of completely or substantially converting the ases of sulphurous acid into sulphuric acid; e remaining residues of the SO2-gases`with this methodof working will be so small that the enclosure succeeding the enclosure for the roduction of acid'will already o rate as a ay-Lussac, that is to say, the aci running oil' from such enclosures will be richerfin nitrosulphonic acid than the acid fed to the several enclo- DI! sures. Moreover, the acid running of from the enclosure` where the production takes place should be so strong in nitrosulphonic acid that at least 25 percent of the amount of u nitrosulphonicacid fedrto said' enclosure re- :95

main in the acid running olf therefrom. This proportion of nitrous vitriol or of Anitrosulphomc acid may however, amount to nine tenths of the original. charge, or, inthe case of a particularly well operating denitrat- 10 meter of the unit should not 65 ing tower being placed before the productionenclosure, it may remain unchanged, that is to say, it would correspond to the strength of nltrosulphonic acid.

A plant, arranged in accordance with the principles, above outlined would be constituted by one denitrating tower, only one tower for the production of sulphuricacid, and a plurality of Gay-Lussac-towers. A decrease in the contents of nitrosulphonic acid will only occur in the denitratingtower in` which the complete denitration of the amount of daily output requiredv for comlnercial acid for the market is effected and in the tower in which the production of acid takes place, while in all other towers of the plant there will be au inerea'se of the contents of nitro-sulphonic acid. The denitrating tower may preferably be of such size, and may be so arranged and constructed that it is of sufficient capacity to not only denitrate the daily output of commercial acid, but also additional quantities of nitrous vitriol or nitro-sulphonic acid. The productiontower on the other hand, will be worked the more favorably, the higher is the .amount of the acid denitrated in the denitrating tower, and the less will be the amount of oxides of nitrogen which are to be liberated in the production-tower, and the acid will therefore run oli' from such tower with a. correspondingly higher content of nitrosulphonie acid. Thereis however, a-maximum limit for the amount of nitrous vitriol or nitrosulphonic acid to be denitrated in .the 4denitrating tower, this limit lbeing attained when original the quantity of oxides of nitrogen evolved,`

expressed in terms of nitric acid of 36 B. amounts to one third of the sulphuric acid it is desired to produce, and expressed in terms of sulphurie acid of B.

As to the Gay-Lussac-enclosure only one tower or a tower-like apparatus will be .found suflcient in many cases, and for ordinary purposes two such towers or enclosures will have to be employed generally.

In the case above referred to, where there is the possibility of denitrating larger guantities of nitrosulphonic acid or of nltrous yvitriol in the denitrating enclosure, the rinsing system is preferably so arranged that the acid, after the withdrawal ofthe connnercial Y production acid, is delivered to the last Gay-Lussac-tower from which it passes to the tower for the production of sulphurlc acid, and thence it is delivered to the denitrating tower. In the'case, however, of the Gay-Lussac" apparatus and the productiontower requirin a larger amount of rinsing acid than could be obtained from the denitrating tower after the withdrawal of the commercial production-acid, the rinsing may be effected in one ofthe ifo lowing two ways. I may eithenproceed by providing an inside circulation fo'r eachof the absorption ters.

towers or Gay-Lussac towers and for the productiontower for the production of sulphuric acid in addition tothe rinsing acid coming from the denitrating tower which latter asses from one tower to theother, so as to o tain the required amount of'rinsing liquor for all of these enclosures; or in another modification, I may proceed by employing a portion of the acid of the productiontower together with the excess acid running olf from the denitrating tower as the circulating liquid for the entire plant.

By providing a gas pressure of 1/4E to 6 (a quarter to six) lmillimeters water column for each vertical or ascending meter of the tower as above outlined, it becomes possible to make such towers, or tower-like enclosures or boxes or tanks of considerably larger cross sectional area than heretofore possible, andfiu consequence thereof plants may be constructed comprising considerably larger units of production than have been employed heretofore for tower-systems or even for chambersystems. In accordance therewith it has become possible to erect plants embodying the towers with diameters of 7, 10 and 14 meters (23%, 323/]t and 46 'feet respectively) 'which would correspond to a cross sectional area without the brick lining of 39, 781/2 and 150 square meters. Nor are these dimensions to be regarded as the maximum limits.

The calculation of the cross sectional area `of the towers required for a certain size of packing material of small size or lfor any other packing means is vgoverned "by the amount of gas to be passed through the system of apparatus. The measure of cross sectional area and the free spaces in the packing material should be adjusted andI selected to correspond to the volume of the gases, and in suclra manner that the resistance above referred to of a quarter to 6 millimeters water columnpressure may be obtained.

The available height, that is to say the heightrof the tower section provided with filling material, should be made to corrcand at an average temperature of about 5() degrees centigrade an available packing section of 4-thousand cubic meters would be required. N ow, with a tower of 14 meters diameter equal to about 150 square meters cross section under the conditions lnentioned the total height required for the available fillinggorpacking space would amount to 27 me- This total height of about 27 meters would have to be distributed over three or four, or even over but two towers.` l

Broadly speaking, in accordance with the principles of my invention hei'gh't and crossl sectional measure of the units of apparatus tion and of the general management of the plant.

The sum of the available heights of the several towers or enclosures serving for the production of the sulphuric acid proper and for the absorption of theL nitrogen-oxides may Le reduced to about 8 meters, as has been ascertained in practical '-working, or

this totalheight may be increased up to 50- meters and more, as has been proved to be of advantage in other cases of practical op. eration. An increase in height ajords the advantage of a prolonged gas passage `with an increased gas-velocity. By this means the gas is caused to be brought in contact and to react with the downwardly trickling liquid, so as to result in` a quicker termination of the reaction.

From practical considerations it will be advantageous to provide for equal cross sectional areas of the product1onenclosure and of the absorption enclosures, and -also to provide similar kinds of packing or filling material and size of packing for both kinds of enclosures. But it is also admissible within the scope of my invention to make the production enclosure for the manufacture of the sulphuric acid of smaller cross sectional measure than the absorption enclosures with the same kind of filling or packing material, or in another modification the productionenclosure may have the same cross section as the absorption enclosures, but a finerkind or distribution of packing material'.` This would result in an increased velocity of the gases and an increased friction in the reaction space.

The strength of the acids to be employed may be kept between 55 and 62 degrees B.; but a strength of from 58 `to. 69 B. has

been found preferable. The water required` in the course of the said sulphuric-acid process is preferably added in the productionV tower in the acid-production stage inlthin jets and, in view of the strength of the' acid in the diferent parts of said tower without substantial liberation 1 of nitrous gases. Other portions of water may beadded in the denitrating tower, and thereby enter the system Vin the gases escaping from said denitrating tower or the like.

The rinsing system may preferably be arranged in such a manner that the acid leavin the productiontower less the amount to e withdrawn as the commercial product is caused to pass onto the last tower or an equivalent enclosure, and thence to the second before tle last and so on as far as t0 lculated between these two enclosures.

the production tower. In case there is but one absorption enclosure besides the pro-I ductionenclosure the acid will only be ciIrthe denitrating tower is adapted to denitrate more acid than would correspond to the quantity to be withdrawn .as commercial product, the excess portion is passed to the last tower or enclosure. In case of a combination of only one'absorption tower with the production tower the admission of Jthe gases from the production tower into the absorption enclosure is preferably effected inV the upper part of the same, so that the gases will give olf their heat to the cooled acid fed to the enclosure, which will facilitate the absorption of the nitric oxids. In the case of employing impure gases one or several washing towers may be arranged before the denitrating tower or between the denitrating tower and the production enclosure.

A particularly favorable result is produced by providing for a subdivision of the gas current into a plurality of small gas jets as the result of packing or filling bodies or granules of about 3 centimeters (1.1 inch) size or less. By Ymeans of this kind of granulated o r similar packing the gas current is spllt up into a great multitude of thin jets Which are compelled to be forced and to emerge between the granules, so that said jets are brought into intimate contact with the rinsing liquid which is finely distributed as a thm coating on the surface of the said granules.

Upon -the accompanying drawing I have illustrated diagrammatically and by way of exemplification the arrangement of the different units of -a plant for the manufacture of sulphuric acid in accordance withthe principles of my invention in vertical elevational view in Figures 1 to 5 of the drawing, showing various modifications to which the invention is adapted without, however, restricting the invention to these particular embodiments vof the principles above outlined which in drawings andin Figures 1 and 2 I have also indicated the percentages of nitrous vitriol in the various stages of operation of the plant. In Figure 1 the method of operation with but one production tower is illustrated, the acid running off from this tower after the withdrawal of the quantity intended for commercial acid being fed to the last Gay-Lussac and asv running ofi' from the productiontower with at least 25% of its original strength.

Figure 2 shows substantially the same arrangement, but with the acid in the productiontower being denitrated down to about 80-100% of the original acid only. These figures also show the increase of the strength of the nitrous vitriol in the following towers. In the modification according to Figure 3 only one Gay-Lussac enclosure is associated with one production tower and one denitrating tower, and the acid may be circulated on said Gay-Lussac-tower. In the modification of Figure 4 two Gay-Lussac-enclosures are employed; substantially the entire output of the production tower may be fed to the denitrating tower from which the alnount in excess of the desired output of commercial sulphuric acid is fed to the last Gay-Lussac tower from which it proceeds towards the front end of the plant as operable nitrosyl-sulphuric acid or nitrous vitriol of proper strength. Figure 5 is a modification with internal circulation of the acid on all or ony some of the enclosures, the entire acid from the productiontower being for in stance fed to the last Gay-Lussac, and the internal circulation provides for the contingency that the acid from the denitrating tower should not be sufficient for the opera` tion of absorption or Gay-Lussac enclosures.

The way of the gases is not indicated in the drawings. The gases first enter the denitrating tower; thence they pass into the productiontower, and after leaving the productiontower they pass into the first, then into the second, and into the third Gay- Lussac enclosure, as the case may be. The rinsing acid passes in the opposite direction. From the first Gay-Lussac enclosure the bulk of the acid flows to the production tower, and a small portion may fiow onto the denitrating tower. The acid running of from the denitrating tower` is withdrawn as commercial sulphuric acid for the market, and the acid running off from the productiontower is returned to the last Gay-Lussac enclosure.

In case of a very good operation of the denitrating tower, that is to say, when the denitrating tower should denitrate more than is required for marketable purposes, the excess of the acid produced therein may also be passed to the last Gay-Lussac enclosure together with the acid running off from the production tower, and as indicated in Figures 4 and 5 of the drawing. These figures also illustrate the modification that the total amount of the acid from the productiontower is fed to the del'iitrating tower from ,Which theacid after the withdrawal of the commercial acid is returned to the last Gayi Lussac enclosure, with the eventuality of circular rinsing, as above explained.

While the arrangements shown are particularly well adapted for furthering the objects ot' my invention, other arrangements may be found useful for carrying out my process, and other modifications are possible within the meaning and the ambit of thc claims hereunto appended.

1. In the art of making sulphurie acid by the nitrogen-oxid method the step of oxidizing sulphurous acid gases which comprises passing said gases and nitrous ,vitriol of at least fifty-five degrees B. strength in the vertical direction in contact with each other and through packed reaction spaces, and regulating the flowing resistance through said spaces, so as to correspond to a pressure ranging from approximately one quarter millimeter to six millimeters water-column forl each meter of said vertical flow, and keeping the nitrous strength of the vitriol at the bottom of said spaces within a limit of at least a quarter of the nitrous strength at the top of said spaces. l

2. In the art of making sulphuric acid by the nitrogen-oxid method the step .of oxidizing sulphurous acid gases which comprises passing said gases and strong nitrous vitriol of at least fifty-five l:degrees B. strength through a comparatively large-sized, relatively densely and irregularly packed uninterrupted reaction space, regulating the iiowing resistance through said space, so as to correspond to a pressure ranging from approximately one quarter millimeter to six millimeters water column for each meter of `said vertical How, keeping the nitrous strength of the vitriol at the bottom of said space within a limit of at least a quarter of the strength at the top of said spaces, and

passing the gases escaping from said space in contact with absorbing sulphuric acid, containing nitrous vitriol. Y

3. In the art of making sulphuric acid by the nitrogen-oxid method the step of oxidizing sulphurous acid gases which comprlses L passing said gases and strong nitrous vitriol of not less than approximately fifty-five de` grees Beaum through a comparatively largesized, densely and irregularly packed uninterrupted reaction space, regulating the fiow- 1 ing resistance through said space, so as to correspond to a pressure ranging from approximately one quarter millimeter to six milliineters water-column for each meter of said vertical tiowfkeeping the nitrous strength of 1 the vitriol at the bottom of said space within a limit of at least a quarter of the nitrous strength at the top of said space, passing the gases, escaping I"from said space in contact with absorbing sulphuric lacid containing 1 nitrous vitriol and feeding said reaction space with the acid produced by saidabsorption.

4. In tle art of making sulphuric acid by the nitrogen-oxid method the step of oxidiz- 1 ingly treating sulphurous-acid gases which comprises passing said gases in contact wlth strong nitrous vitriol and in the vertical d1- rection through substantially closely packed large uninterrupted reaction spaces presenting a resistance to the flow of the gases and vitriol which is equivalent substantially to a pressure of from one quarter millimeter to about six millimeters for each vertical meter of said packedreactionspaces,keeping the nitrous strength of the vitriol owing olf from said spaces within at least a quarter of the nitrous strength of the vitriol fed to said spaces, absorbing the then escaping gases in sulphuric acid eontaining nitrous v1tr1ol and re-using the vitriol thus obtained for the feeding of the said reaction spaces and for said absorption.

5. In the art of making sulphuric acid by the nitrogen-oxid method the method comprising the passing of sulphurous acid gases in oxidizing contact with strong nitrous vitriol of sulistantially 55 degrees B eaum strength in the vertical direction and 1n substantially closely packed uninterrupted reaction spaces containing substantially grans ular packing material, keeping the nitrous strength of the vitriol running oif from such r spaces within at least a quarter of the n1- trous strength of the vitriol fed thereto and the resistance to flow in the packed -reaction spaces -at at least a quarter of a millimeter pressure for each vertical meter of packed reaction space, absorbing the gases, escaping from said reaction spaces in sulphuric a c1d containing nitrous vitriol, and re-circulatmg the nitrous vitriol in the reaction spaces and the nitrous vitriol obtained by absorption 1n contact with the gases and gaseous reaction products. I

6. In the art of making sulphuric acid the A method which comprises passing sulphurous acid gases in oxidizing contact with nitrousv vitriol in the vertical direction through large closely packed uninterrupted acid production spaces, keepingthe nitrous strength of the nitrous vitriol flowing off from said spaces within at least one quarter the nitrous strength of the vitriol fed to said spaces, passing the gases escapingcfrom the production spaces through large absorbing spaces in contact with sulphuric acid containing nitrous vitriol, feeding part of the liquid flowing oi from the production spaces to the absorption spaces, -and denitrating the balance of the liquid from said production spaces, and feeding nitrous vitriol discharged :Erom the absorption spaces into the production spaces.

7. Inthe art of making sulphuric acid thev A method, which comprises passing sulphurous acid gases in 'oxidizing contact with nitrous d vitriol of at least about 55degrees Beaum strength through a large, substantially close- 1y packed reaction enclosure, keeping the taining nitrous vitriol thereby absorbing said escaping gases in said sulphuric acid, and feeding the thereby resulting absorption acid to the other enclosure.

8. In the art of making sulphuric acid thev method, which comprises passing sulphurous acid gases in oxidizing contact with strong nitrous vitriol of at least fifty-live degrees B. strength through a substantially closely packed large voluminous uninterruptedreaction enclosure, presenting a resistance to.

the How equalizing a pressure of about one quarter millimeter to about six millimeters water column for each vertical meter of reaction enclosure, keeping the nitrous strength of the vitriol iowing off from said enclosure Within at least a quarter of the nitrous strength of the vitriol fed thereto, passing the gases escaping from said enclosure in contact with sulphuric acid, thereby absorbing said gases and forming nitrous vitriol andv feeding the thus obtained nitrous vitriol to the reaction enclosure. v

9. In the art of maln'ng sulphuric acid the method, which comprises passing sulphurous acid gases in oxidizing contact with strong nitrous vitriol of at least-55 degrees Beaum strength and through a substantially closely packed uninterrupted reaction enclosure, preventing full denitration of the nitrous vitriol at the bottom of said enclosure, passing the gases escaping from said enclosure in absorbing contact with sulphuric acid in absorbing enclosures, re-circulating the whole of thenitrous vitriol and the sulphuric acid respectively in said enclosures, feeding the sulphuricacid with the absorbed gases from the last mentioned enclosures to the reaction enclosure, and denitrating vitriol-liquid running of from the reaction ,enclosure outside of said enclosure. `1

10. -In the art of making sulphuric acid the method which comprises passing sulphurous acid gases in oxidizing contact with through an absorption enclosure less densely packed than the reaction enclosure' andin contact with absorbing sulphuric acid, thereby absorbinY said gases and formin nitrous vitriol, fee ing the thus obtaine nitrous vitriol to the reaction enclosure, and denithe nitrous 'strength of theilo the method which comprises passing sul# phurous acid gases in oxidizing contact with strong nitrous vitriol in the vertical direction and in contact with substantially granular packing material in a reaction enclosure, keeping the nitrous strength of the liquid flowing off from said enclosure within at least a quarter of the original' nitrous strength of said nitrous vitriol, passing the gases escaping from said reaction enclosure through and in contact with absorbing sul- .phuric acid and re-circulating the said escaplng gases in contact with said absorbing acid,

thereby producing nitrous vitriol, feeding said vitriol to the reaction enclosure, and denitrating liquid from the lower part of said reaction enclosure outside of said enclosure. 12. In the art of manufacturing sulphuric acid causing sulphurous acid gases of comparatively moderate temperature to react upon nitrous vitriol` of at least degrees B. strength in tower-like enclosures of at least 210 square feet sectional area each, malntaining a nitrous strength of at least one quarter the original nitrous strength in the acid running off from said enclosures, denit-rating the acid produced in some of said enclosures and feeding the acid from the rest of said enclosures and the gases evolved to- Y gas absorbing spaces.

13. In the art of manufacturing sulphuric acid causing sulphurous acid gasesto react at about fifty degrees centigrade upon nitrous vitriol of at least 55 degrees B. strength in umnterrupted spaces of at least 210 square feet sectional area each, maintaining a ni trous strength of at least one quarter the original strength in the acid running olf from said spaces, enitrating part of said runoff acid, and absorbing the gases resulting thereby and the gases from said uninterrupted spaces. in nitrous vitriol.

acid causing sulphurous acid gases to react at about fifty degrees centigrade upon nitrous lvitriol of at least`55 degrees B. strength within a packed uninterrupted reaction space of large extent of at least 210 uare feet sectional area, denitratng some o the acid produced, allowin lthe gases evolved in said reaction space an those resulting from Cthe denitration to flow in contact with new quantities of absorbing nitrousvitriol both in a downward direction, and denitratng part of the acid thereby produced together with the acid above mentioned.

15. In the art of manufacturing sulphuric acid causing sulphurous-acid gases at moderate temperature of substantlally fifty degrees centigrade to react upon nltrous vitriol of at least 55 degrees B. strength within a 14. In the art of manufa,cturing'lsulphuricV large packed and uninterrupted reaction space of at least 210 square feet sectional area, maintaining the nitrous strength of the acid discharged from said space, so as to amount to at leastJ one quarter of the original nitrous strength of nitrous vitriol, ydenitrating part of said run-off nitrous vitriolcontaining acid, causing the gas evolved in said reaction space and by denitration to flow inthe downward direction together with absorbing nitrous vitriol in a plurality of serially arranged communicating enclosures, and causing the entire amount of nitrousvitriol-acid present in some of said last mentioned enclosures to re-circulate several times through the respective enclosures.

V16. In the art of manufacturing sulphuric acid causing sulphurous acid gases at moderate temperatures of substantially fifty degrees centigrade to react with very large volumes of nitrous vitriol of at least 55 degrees strength Within a packed large uninterrupted reaction space of an extent much in excess of the reacting sulphurous acid gases, maintaining the nitrous strength of the acid discharged from said space at notless than one quarter the original nitrous strength of the vitriol, denitratng part of said discharged acid together with additional amounts of nitrous vitriol, acting with the evolved gases upon separate quantities of absorbing nitrous vitriol in a downward direction and circulating said .gases in .contact with said absorbing vitriol vfrom the last towards the first of said quantities of vitriol in corresponding communicating separate euclosures.

HUGO 'PETERSEN 

